The Supreme Court's unusual hearing Wednesday on the role corporations can play in influencing elections carries the potential not only for rewriting the nation's campaign finance laws but also for testing the willingness of the court led by Chief Justice John G. Roberts Jr. to defy the decisions of Congress and to set aside its own precedents.

The court will consider whether the "proper disposition" of a case -- pitting a conservative group's scorching campaign film about Hillary Rodham Clinton against federal campaign finance laws -- requires overturning two decisions that said government has an interest in restricting the political activities and speech of corporations.

That raises ageless questions about the role of stare decisis -- the court's custom of standing by its previous decisions. But it also raises new ones about the boldness of a court that has moved to the right with the addition of Roberts and Justice Samuel A. Alito Jr.

"Everyone knows this is a case about the chief and Justice Alito," said Richard J. Lazarus, co-director of the Supreme Court Institute at the Georgetown University Law Center. "And the real question here is whether the chief is ready to pull the trigger" on declaring the restrictions unconstitutional.

Roberts's instincts have been to move incrementally, Lazarus noted. But such a narrow and consistent chipping-away approach -- Roberts and Alito have voted for every challenge to campaign finance laws since joining the court -- may simply be a way to make more-sweeping decisions appear inevitable.

"I don't think people should underestimate the chief justice's ability to look down the road," said Washington attorney David C. Frederick, who frequently argues before the court. "I think he's got a larger constitutional vision. He's relatively young and looking into the future."

As the recent hearings on new Justice Sonia Sotomayor showed, pledging allegiance to stare decisis is a staple of the modern confirmation process for a Supreme Court nominee. Jeff Sessions of Alabama, the ranking Republican on the Senate Judiciary Committee, said he decided to vote against the judge from New York because he did not think she could resist the "siren song" of judicial activism.

To that end, those who favor strong government controls on campaign finance, such as Democracy 21's Fred Wertheimer, say Roberts should stand by his own words about how careful the court should be in overturning precedent.

"It is not enough that you may think the prior decision was wrongly decided," Roberts said at his confirmation hearing. "That really doesn't answer the question; it just poses the question."

Instead, he said, justices must "look at these other factors, like settled expectations, like the legitimacy of the court, like whether a particular precedent is workable or not, whether a precedent has been eroded by subsequent developments."

There are two precedents at stake in Wednesday's rehearing of Citizens United v. Federal Election Commission. One is the court's 1990 decision in Austin v. Michigan Chamber of Commerce, in which it upheld a state law that said corporations could be barred from spending their profits to urge a candidate's election or defeat.

The second is part of the 2003 decision upholding Congress's Bipartisan Campaign Reform Act, commonly known as the McCain-Feingold campaign finance law. The court ruled 5 to 4 that Congress may curtail corporate spending on advertising that mentions a candidate shortly before an election, even if it does not explicitly support or oppose that person.